The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Refrigeration and air conditioning systems of the aforesaid type, whose coolant circuit also has a compressor and a liquefier in addition to the expansion valve and the evaporator, are known in the most varied embodiments from the prior art and are used, for example, for the cooling of food or for the air conditioning of rooms. It is necessary for a continuous, efficient and problem-free operation of refrigeration and air conditioning systems of this type to regularly defrost the evaporators which are used in each case and which ice during operation. It is an aim in this process to carry out the defrosting procedure as fast as possible in order not to expose food cooled in a refrigeration system, for example, to increased temperatures for an unnecessarily long time.
During the defrosting procedure, the coolant flow present in the coolant circuit has to be diverted or interrupted by means of hot gas or cold gas during the defrosting in order thus to make it possible for the hot gas or cold gas used for the defrosting to be able to be guided through the evaporator and optionally through the expansion valve. When defrosting via the ambient air or via an electrical defrost heating, the coolant flow does not necessarily have to be diverted, but must at least be interrupted so that the evaporator is not cooled by the coolant during the defrosting procedure, which would counteract the defrosting procedure.
The interruption or diversion of the coolant flow during the defrosting procedure is usually effected by solenoid valves which are located at a suitable position in the coolant circuit, with the position of the named solenoid valves being able to be disposed either close to the evaporator or also relatively far away from the evaporator in many applications.
It must furthermore be ensured during the defrosting procedure, if electronic expansion valves are used, that the latter are moved into a static state. If, namely, the regulating or control procedure present during normal operation were continued during defrosting, this could result in damage to the expansion valve since the latter is not designed for a dry run present during the defrosting procedure. Furthermore, a control or regulation of the expansion valve continued during the defrosting procedure would result in irritating noise pollution.
It is necessary in this respect that the control device associated with the electronic expansion valve is in each case informed of when a defrosting procedure starts and ends since it can otherwise not move the expansion valve into a static state. If the solenoid valves for the interruption or diversion of the coolant flow during the defrosting procedure are located close to the control and regulation device associated with the expansion valve, an electrical connection can be established between this device and the solenoid valves via which the named information is transmitted. In many applications, however, as already mentioned, the solenoid valves are arranged spatially far away from the control and regulation device associated with the expansion valve so that the establishment of an electrical connection is difficult or associated with a disproportionate effort. An application of this type is present, for example, in a supermarket with a plurality of freezers, where at least one electronic expansion valve is located with its respectively associated control device inside each freezer and the solenoid valves for the interruption or diversion of the coolant flow are accommodated centrally in a control room which is located comparatively far away from the freezers.